Search results for "RADIATION"
showing 10 items of 5298 documents
ALANINE/ESR DOSIMETRY FOR TOTAL BODY IRRADIATION USING AN ANTHROPOMORPHIC PHANTOM
2016
Introduction: Total Body Irradiation (TBI) is a technique widely used in the radiation blood-oncology in the treatment of patients that need bone marrow transplantation or peripheral stem cell transplantation. This technique has some limitations such as the lack of homogeneity of the dose distribution (which may show variations of 20% in the different areas), irradiation of critical organs such as the lungs, the liver, the intestine and the eye-lens which can receive a dose comparable to that nominal and require appropriate shielding and a proper evaluation of the dose absorbed by them. The positive outcome of this type of radiation therapy is strictly related to a precise and accurate meas…
Comparison of EPR response of alanine and Gd2O3-alanine dosimeters exposed to TRIGA Mainz reactor.
2015
In this work we report some preliminary results regarding the analysis of electron paramagnetic resonance (EPR) response of alanine pellets and alanine pellets added with gadolinium used for dosimetry at the TRIGA research reactor in Mainz, Germany. Two set-ups were evaluated: irradiation inside PMMA phantom and irradiation inside boric acid phantom. We observed that the presence of Gd2O3 inside alanine pellets increases the EPR signal by a factor of 3.45 and 1.24 in case of PMMA and boric acid phantoms, respectively. We can conclude that in the case of neutron beam with a predominant thermal neutron component the addition of gadolinium oxide can significantly improve neutron sensitivity of…
Caracterización de barita cubana y su reducción carbotérmica en horno de microondas
2007
The Cuban Barite (BaSO4) is characterized by X ray diffraction, chemical analysis and scanning electron microscopy. The principal components are identified and its characteristic morphology is shown. Its carbothermic reduction under microwave irradiation is carried out with the purpose of to improve the yield of this stage during the mineral transformation process in reagent of barium of diverse applications. La barita cubana (BaSO4) se ha caracterizado por difracción de rayos X, análisis químico y microscopía electrónica de barrido. Se han identificado sus componentes mayoritarios y así mismo se muestra su morfología característica. Se ha realizado su reducción carbotérmica en horno de mic…
Primary mouse fibroblasts deficient for c-Fos, p53 or for both proteins are hypersensitive to UV light and alkylating agent-induced chromosomal break…
2000
The important regulatory proteins, c-Fos and p53 are induced by exposure of cells to a variety of DNA damaging agents. To investigate their role in cellular defense against genotoxic compounds, we comparatively analysed chromosomal aberrations and apoptosis induced by ultraviolet (UV-C) light and the potent alkylating agent methyl methanesulfonate (MMS) in primary diploid mouse fibroblasts knockout for either c-Fos or p53, or double knockout for both genes. We show that c-Fos and p53 deficient fibroblasts are more sensitive than the corresponding wild-type cells as to the induction of chromosomal aberrations and apoptosis. Double knockout fibroblasts lacking both c-Fos and p53 are viable an…
Waveguiding properties of a photonic crystal fiber with a solid core surrounded by four large air holes
2009
The polarization-dependent guiding properties of a hexagonal-lattice photonic crystal fiber with a solid-core surrounded by four large air holes are investigated. The appearance of a polarization dependent cutoff frequency, together with several parameters as the birefringence, the modal effective area, the group velocity dispersion and the polarization dependent loss are analyzed. A collection of fibers with different structural parameters were fabricated and characterized. An effective anti-guide structure from at least 450 nm to 1750 nm, a polarizing fiber with a polarization dependent loss of 16 dB/m at 1550 nm, and an endlessly singlemode polarization-maintaining fiber with group biref…
ChemInform Abstract: Non-Conventional Methods and Media for the Activation and Manipulation of Carbon Nanoforms
2014
Very often, chemical transformations require tedious and long procedures, which, sometimes, can be avoided using alternative methods and media. New protocols, enabling us to save time and solvents, allow us also to explore new reaction profiles. This Tutorial Review focuses on the physical and chemical behavior of carbon nanoforms, CNFs (fullerenes, nanotubes, nanohorns, graphene, etc.) when non-conventional methods and techniques, such as microwave irradiation, mechano-chemistry or highly ionizing radiations are employed. In addition, the reactivity of CNFs in non-conventional media such as water, fluorinated solvents, supercritical fluids, or ionic liquids is also discussed.
Measurement and correction of atmospheric effects in O<inf>2</inf>-B and O<inf>2</inf>-A absorption bands in the context of s…
2014
Under sun-light illumination, the shape of the atmospheric oxygen bands (O 2 -B, 687 nm and O 2 -A, 760 nm) of the vegetation radiance is modified by chlorophyll fluorescence. However for far-range measurements, atmospheric effects also modify this shape. In this study, measurements in O 2 -A and O 2 -B absorption bands have been performed at different altitudes up to 3123 m over bare soil and wheat fields. It is observed that bands depth increase significantly with altitude. In O 2 -B band, the total magnitude of variation is of the same order of magnitude as the change induced by vegetation fluorescence, while it is much greater in O 2 -A band. We used MODTRAN 4 to correct measurements fr…
The F-type centres in YAG crystals
2001
The comparative study of optical properties of thermochemically reduced undoped YAG (Y3Al5O12) crystals is reported. A particular type of the centres often observed in YAG crystals synthesized as w...
Blue luminescent amino-functionalized graphene quantum dots as a responsive material for potential detection of metal ions and malathion
2022
Large amounts of hazardous and toxic substances in the environment require non-toxic, cheap, easy, rapid, and sensitive methods for their detection. Blue luminescent graphene quantum dots (GQDs) were produced by electrochemical cleavage of graphite electrodes followed by gamma irradiation in the presence of ethylenediamine (EDA). Modified dots were able to detect metal ions (Co2+, Pd2+, Fe3+) due to photoluminescence quenching. The highest sensitivity was detected for the sample irradiated at a dose of 25 kGy. The limits of detection (LODs) were 1.79, 2.55, and 0.66 μmol L−1 for Co2+, Fe3+, and Pd2+, respectively. It was observed that GQDs irradiated at 200 kGy act as an ultra-sensitive tur…
Reduction of Dinitrogen to Ammonia in Irradiated Heterogeneous Systems
1988
The recent developments of the research in the field of dinitrogen reduction to ammonia at mild conditions of pressure and temperature are reported. After a brief historical recapitulation of the traditional thermal process, the new routes for NH3 synthesis (biological photosynthesis, direct electrochemical reduction, and photocatalytic reduction) are presented and critically discussed. A particular attention is devoted to heterogeneous photocatalytic reduction performed by irradiating pure, mixed, and doped semiconducting catalysts in gas-solid and liquid-solid systems. The fixation of dinitrogen in aqueous solutions containing complexes and photoactive particulate systems is also reported…